1. Technical Field
The invention relates to suspension systems, and in particular to an air suspension system used for vehicles. More particularly, the invention relates to an air spring having an auxiliary reservoir formed in one of the end members of the air spring which communicates with the main air chamber of the air spring to enable the spring rate to be varied by providing communication between the main air chamber and auxiliary reservoir.
2. Background Information
Air springs have been used for a considerable number of years for various applications including use in vehicles for suppressing road shock imparted onto the wheels of a vehicle upon the wheel encountering a projection or depression in the roadway.
Each air spring will have a specific spring rate depending upon the design of the air spring components and its size which will provide various ride characteristics for the vehicle in which the air spring is mounted. One of the factors which determines the spring rate is the volume of the air contained within the flexible sleeve or bellows of the air spring which forms the main air chamber. Varying the volume of air in the flexible sleeve of the air spring enables various spring rates to be achieved. This can be accomplished by various means such as by supplying or removing air into or from the air spring by various control valves, and by the use auxiliary air reservoirs which are fluidly connected to the main air spring chamber. When a vehicle wheel encounters a depression or projection in the roadway, air will be introduced into or removed from the air spring by means of an auxiliary reservoir to change the volume of air, thereby changing the spring rate in order to provide the desired ride characteristics for the vehicle. The smaller the volume of the air chamber, the firmer will be the ride provided thereby.
Heretofore auxiliary reservoirs for air springs usually consisted of a remotely mounted reservoir which was connected by a hose or other fluid communication line to the air chamber of the air spring. Some examples of such prior art air springs containing auxiliary reservoirs are shown in U.S. Pat. Nos. 2,115,072, 3,039,761, 4,159,105, 4,592,540, 4,743,000, 5,169,129, and 5,413,316.
Other air springs use a dual chamber type of arrangement in which an auxiliary reservoir is formed in the air spring and communicates with the air spring through various controlled openings. Examples of these prior art dual chamber air springs are shown in the following patents.
U.S. Pat. No. 4,592,540 discloses a combination air spring/damper in which an actuator has two functions, one to adjust the shock absorber and one to open the path to the second chamber. However, there is no mechanism for regulating air into the main air spring. It also requires additional complicated mechanisms and openings and is in two separate chambers, not one contained within another as in the present invention. Likewise, the two chambers are welded together in a complicated arrangement and could give rise to leakage of air to the outside of the air chamber whereas in the present invention any leaks in the auxiliary chamber will leak into the main chamber and has little effect on the operation of the invention.
U.S. Pat. No. 4,598,929 shows a combination air spring/hydraulic damper in which the auxiliary air spring is mounted above the main air spring and its fluid communication therewith is controlled by a piston rod and a control rod contained in the piston rod of the hydraulic damper. One actuator operates the spring with two separate chambers and it uses one control rod for both the air spring and shock absorber and it is concerned with the ability to change the spring constant and damping in motion to control the ride of the vehicle.
U.S. Pat. No. 4,666,135 discloses an air suspension system having an air spring/damper combination, an auxiliary reservoir, and a control valve which is rotated by a motor and gear combination for providing selective communication between the auxiliary air chamber and main air chamber of the air spring. It does not use a controlled plunger for regulating the flow of outside air into and out of the air spring as in the present invention.
U.S. Pat. No. 4,697,796 discloses an air spring/hydraulic damper combination in which the air spring has two chambers and uses an electric motor for rotating a shaft to provide communication between the pair of air chambers to change the effective volume thereof.
U.S. Pat. No. 4,735,401 discloses a shock absorber having a plurality of air chambers which are connected and disconnected with each other by a rotary valve which is controlled by an actuator mounted on top of the air spring. However, the control does not regulate air into the air spring assembly as does the present invention nor does it use a plunger mechanism of a solenoid for assisting in retaining a partition plate to form the auxiliary reservoir.
U.S. Pat. No. 4,844,428 shows another air spring having a main and auxiliary air chamber which are in fluid communication with each other by use of an electric motor and a piston for controlling the fluid opening between the various air chambers. The piston/motor does not open or close a chamber as in the present invention and it adjusts volume in the always open chamber. it also requires a more elaborate linear positioning motor, motor controller, screw drive, and bearing to operate and does not indicate how the air is regulated into and out of the air spring.
However, none of these prior art suspension systems which utilize two or more air chambers for effecting the air spring rate, provide for connecting the air spring to a remote source of pressurized air, such as the compressor found in many vehicles utilizing the air spring and which utilizes the plunger of a control valve for securing a partition plate within the end member of the air spring to form the auxiliary reservoir.
The present invention provides an air spring for vehicle suspension systems having a main air chamber formed by a flexible bellows and an auxiliary air chamber formed in one of the end members thereof which is in selective fluid communication with the main air chamber to change the effective volume for changing the air spring rate.
The air spring of the invention uses a partition plate mounted in the interior of a usual end cap to form the auxiliary chamber, which plate is retained in the end cap by a plunger mechanism of a solenoid valve which is connected to a remote source of pressurized air wherein the plunger can be rotatable or linearly moveable for selectively providing communication between the auxiliary air reservoir and main air chamber or for supplying fluid communication between the supply of compressed air and the main air chamber.
Another aspect of the invention is forming the end cap of high strength glass reinforced material with the partition plate being snap-fitted therein and retained by the control valve.
A further feature of the invention is to provide a solenoid with two separate independently moveable plungers and actuation coils for controlling the flow of air between the auxiliary reservoir and the main air chamber and between the main air chamber and the remote source of pressurized air.
Still another aspect of the invention is to provide the end cap with a plurality of auxiliary air chambers which are fluidly connected with each other or with the main air chamber through a solenoid controlled plunger, wherein partitions are mounted in the end cap by snap-fit engagements with a housing of the plunger, thus enabling the partitions to be formed of various materials with the solenoid assisting in locking the partitions in position within the end cap.
Another feature of the invention is enabling the auxiliary air chamber to be formed within a usual end cap without extensive modifications thereto and without affecting the overall height and dimensions of the air spring, thereby enabling the dual rate characteristics to be achieved without extensive modifications and expense.
The dual rate air spring of the present invention also enables the air spring to operate in its usual manner wherein air is introduced into and out of the main air chamber of the flexible bellows from a remote source of air without use of the auxiliary reservoir until the same is required, at which time a selective movement of the solenoid plunger will provide the desired communication between the two air chambers and/or stop the flow of air from the remote source.
The foregoing advantages, construction, and operation of the present invention will become more readily apparent from the following description and accompanying drawings.